Perhaps I misunderstand the unity horn, but I did not mean my suggestion to depend on summation: the idea simply is that one horn flows directly into the other, rather than being discrete; you could have the bottom or top half alone. So the profile is still tractrix (say) it is just that it merges smoothly into its neighbour. The drivers need not be any further apart than they are in a conventional horn system configuration. Would that not work?

It does matter how you want to intellectually dissect your example, it is in principle still a summation device. In order to get a flat frequency and phase response, the output from each driver must sum correctly at their crossover point. Your example only differs from the unity horn in the driver locations. There will not be anything approaching continuity between the drivers because they are multiples of wave lengths apart at their perspective crossover points.

I know you have built tapped horns yourself, JLH, but have you tried the synergy horn approach and seen how it compares with conventional horns? Danley's kit seems to be targeted at large venue high power applications, so hard to know how it would deal with low power SETs of the kind we are interested in.

Low power set should not be a problem. The Unity was fine with SET amplifiers, so the Synergy should be no different, if not better. The Synergy horn is different than the original Unity horn. There are some very specific improvements in the Synergy horn, so significant that another patent covers it. See following link for Synergy horn patent application:

Sorry for the long link – just click or copy and paste into your internet address bar.

Anyway, the thing that sets the Synergy apart from the Unity is its phase coherence. This is achieved through some very specific design steps.

1.) The mid or low frequency driver(s) that tap into the horn are electrically bandwidth limited (crossover) below the point where you get the first high frequency cancellation notch. The cancellation notch is created when the distance from the tap point to the apex (compression driver voice coil) is equal to half a wavelength. Some clarification is needed here. This is really not an actual physical distance, but an acoustical distance. This is because the apparent acoustic center of the compression driver and the mids/low drivers do not occur at the voice coil. However, it is not too hard to figure this out with the help of AkAbak simulation software.

2.) The cross sectional area where the mids/lows tap into the horn is such that the circumference is equal to or less than one wavelength of the highest frequency you want it to produce. For example, if your mids tap into the horn where the cross sectional area is 93.5 sq cm, then you would not want to have it produce anything above 1KHz.

3.) The tap point of the mids/lows must have a local expansion rate equal to, or lower than the lowest frequency to be produced. For example, if you want the mid to produce down to 300Hz, then the flare rate at the tap point looking forward toward the mouth must look like a 300Hz or lower flare rate.

4.) The ports or ducts that the mids/lows tap into are not cylindrical in shape. Either they appear as conical, or as a counter bore shape. They are described as being frustoconical in the patent application. This greatly reduces the acoustical impedance of the ports, so you can use a smaller diameter port without running into compression problems. Long and large diameter ports decrease bandwidth and SPL which are things we are trying to avoid.

Overall, the Synergy design is a substantial leap in performance over a Unity. I have played around with a Unity model a few times. I never came up with a completed project. However, with the new design criteria now available from the Synergy patent I am more inclined to try it again. Even my quick and dirty attempt had some sound qualities that were very inviting. The point source and constant directivity behavior was very pleasing. It did not have any of the problems associated with multiple horns such as lobbing and narrowing directivity.

Inclosing, I heard the Danley SH-50 at a dealer in Pennsylvania. It was shocking how coherent it was. The intelligibility and how it was able to flesh out details and separate all the sounds was very surprising. Each sound came from a stable and correct position from within the sound stage. I might say it sounded almost too hi-fi to me. Of course personal preference will play into this. However, I can see people using this speaker in their HT setups with excellent results.

John, I have to confess that I feel very not easy about the idea of Synergy horn. I did not hear the Danley Synergy horns and I have very superficial understanding of what he is trying to do with the whole Synergy/Unity idea. The whole idea does not make very horny, pun intended….

One of the theoretical premises of my understanding of horn loading is for any given loading application there is an infinitely-small bandwidth of “ideal loading”. The “ideal loading” is not a field but rather a single point similar to antiskating with pivoted tonearms. A perfectly balance antiscating is a single point on the records, everywhere else are just acceptable compromises. The same is with horns. I given single frequency has own “perfect horn” with max horn EQ, minimum acoustic low-passing and best possible other characteristics. A deviation from this “perfect narrow frequency” makes acceptable compromises. It does not mean that a horn cannot serve 5-6 octaves but the level of acceptable compromises becomes a bit wider as the driver at lower knew stops acknowledge the horn and at higher knee become too much restricted by the horn size. Again, not saying that it is unusable but I am just explaining the concept.

Not let look at the Synergy design. Let leave aside the way how Mrr. Danley proposes to integrate the drivers and let look at the Synergy idea only from a perspective of best horn for a best given driver. We would see that the mid drivers in Synergy might have own “best” lording but the high and low drivers do not. The LF driver looks like loaded into an insufficient re-entry horn and the HF drivers see also very far from optimum horn. Is it a too high price to pay for point source, particularly considering that I do not support the notion that a point source is necessary better than 3D source?

First let me say I am NOT trying to promote the Synergy horn. I just think it is very intresting to look at and to think about.

Ideal loading only occurs at a singular frequency within any horn. This ideal loading point is where the length is 1/2 a wavelength and the circumference is equal to 1 full wavelength. Since the acoustic size of the wavefront is exact in relation to the horn, ideal loading occurs. Any frequency above or below this is not being loaded in an ideal way. Therefore, there is not a horn that exists that can achieve ideal loading across the horn’s whole bandwidth. In addition, there is no such thing as the perfect driver for a horn. There is only a singular frequency point there a driver will be perfect for the horn it is mounted to. (I'm not discussing Tone, just loading) All drivers mounted into all horns are compromises as soon as they play any frequency that is not exact fitting. So, to me the whole ideal loading thing is a moot point.

I do not believe you fully understand what Danley is doing with the Synergy horn. Each driver is loaded in the most idea way with the least amount of compromises. A curved wall horn holds the same flare rate throughout its entire length, a conical horn does not. The reason why Danley uses a conical horn is its variable flare rate nature. At the apex (throat) of the horn, the flare rate is fast. As you progress closer to the mouth, the flare rate decreases. This high flare rate at the apex (throat) is ideal for loading the compression driver. The mids are mounted further down the horn where the flare rate is appropriately slower for their operation and this continues for the lows.

Real world example of the flare rates inside of Danley SH-50: the SH-50 is a 50 degree conical horn. The mids tap into the horn at around 2.78 inches. The distance from the compression driver’s diaphragm to the mid tap point totals 3.66 inches. The area of expansion is from 0.24 square inches to 11.29 square inches. This equates to a flare rate of 1132Hz loading the compression driver. The electrical crossover is around 1200Hz, so the compression driver is operating within a very ideal way. Since the wavelengths within the compression driver’s range are acoustical small in relation to the rest of the horn, it’s sound is not harmed by the rest of the horn. The same is true for the mids and lows. I have ran through the math it all adds up.

Each driver injects into the horn where the most ideal loading should occur. This also leads to the minimal phase nature of the Synergy horns. This makes the Synergy less of a compromise than a multi horn stack. I understand your underlying feelings about a multi driver horn like the Synergy. I too felt like everything we know about horn purity is being violated. However, Danley’s careful choices have resulted in a very well designed, measured, and sounding horn. I cannot argue with what my ears heard. In the end I did not believe that it is worth arguing about a horn just because its design features do not mesh well with our preconceived notions. We should just let things be the way they are and take them for what they are. I find the Synergy very intriguing. It does a lot of things very well. Would I use it in my own audio? Probably not because it is too clean and hi-fi sounding for my taste. I like my horn colorations too well. Should DIY people try to make their own Synergy? No-it is too complicated and cost too much.

I do not believe you fully understand what Danley is doing with the Synergy horn.

Nope, I do not. Well, I understand it but I am not willing to acknowledge that I understand it as the Synergy horn idea looks too freakish to me. You do not see me arguing the Synergy idea I just feel no interest. I might feel an interest in the Danley’s creatively but to me the even to look at the Synergy horn is scare.

JLH wrote:

Real world example of the flare rates inside of Danley SH-50: the SH-50 is a 50 degree conical horn. The mids tap into the horn at around 2.78 inches. The distance from the compression driver’s diaphragm to the mid tap point totals 3.66 inches. The area of expansion is from 0.24 square inches to 11.29 square inches. This equates to a flare rate of 1132Hz loading the compression driver. The electrical crossover is around 1200Hz, so the compression driver is operating within a very ideal way. Since the wavelengths within the compression driver’s range are acoustical small in relation to the rest of the horn, it’s sound is not harmed by the rest of the horn. The same is true for the mids and lows. I have ran through the math it all adds up.

Are you sure that the same is for the mids and lows? Do not take to account the fact that within the 5.56 inches the mids work as a re-entry path. Also, I do not know how you can talk about math. Any geometry implies distance and distance implies two measuring points. In case of horn if we do not consider the re-entry paths then we have only two absolute points of distance: throat and mouth. We have a curve between them but it is not important. So, I we have a driver sitting on axes then we have a relation between the distances as the driver axes is the same as the horn axes and the driver’s exit points are equidistant to the mouth’s distances. How we have a driver that sits in the mid of the horn, with an angle of 50 degree to the horn axis. The driver has own dimensions, let say 4” diameters of cone. So, what the hell would be “geometry” in case of this application. We have 4” smudge that describes the arrival time from the driver to the edge of the horn, then we have the re-entry reflections that smear the “distances” and “geometry” even more. I do admit that I might not understand something but I just too afraid to look in the theory of the Synergy deeper as I begin to ask myself questions that I have no answers. For instance you say that “electrical crossover is around 1200Hz, so the compression driver is operating within a very ideal way”. Ok, is it a crossover of 64dB per octave? If not then will the Synergy idea to choke with innermodulations?

JLH wrote:

However, Danley’s careful choices have resulted in a very well designed, measured, and sounding horn. I cannot argue with what my ears heard. In the end I did not believe that it is worth arguing about a horn just because its design features do not mesh well with our preconceived notions. We should just let things be the way they are and take them for what they are. I find the Synergy very intriguing. It does a lot of things very well. Would I use it in my own audio? Probably not because it is too clean and hi-fi sounding for my taste. I like my horn colorations too well. Should DIY people try to make their own Synergy? No-it is too complicated and cost too much.

Well, if what you say is true, even if I do not understand it, then perhaps there is no need to argue with Synergy idea but rather to heir Danley to built a set of Synergy system that would have more advanced demands then PA systems, dunk rock-n-roll punks and QSC Audio amplification. If Dan Danley feel that his Synergy is potent to do good sound then it would be interested if he come up with home-targeted products, with “expensive” drivers and upscale demand for sound. It might be not his cap of tea (and I would not blame him) but since the proof is in a pudding it is very unlikely that a listening session in Guitar Center would pick my interest. Do you know if he does custom work? It is not something that I am interested but someone might find it worth to investigate….

I’m absolutely certain that the mids and lows are designed in the same function supporting fashion as I described the compression driver. Danley explicitly explains this in his patent. For my own amusement, I went through all the math and calculations and everything fell in place with what is described in the patent. The Synergy horn meets all 4 points I wrote about in my earlier post about how the Unity and Synergy are different. There is nothing scary about the Synergy, it’s just different. I can understand you may not have any desire to understand it, but that does not mean it is any less a horn.

As you know I’m well aware of the geometry and math involved in analyzing horn designs. You can’t ignore the “re-entry” paths just because it is more challenging to understand. The smearing and reflections you alleged to don’t exist. The mids and woofers operate in laminar flow and not as direct radiation into the horn. The axis of entry is irrelevant because of this. The sound emanates into the horn very much like a balloon inflating. All the re-entry ports are equal distant from one another, therefore the individual pressure wavefronts converge at the same time to construct a single in-phase wavefront that travels toward the mouth.

The crossover is not a specific slope or type. The crossover between the drivers is whatever is required to maintain phase, time, and frequency coherence. The crossovers should be thought about more like transfer function modifiers. This too is explained in the patent.

I agree that the Synergy is interesting to investigate. Danley Sound Labs does do custom finishes on its existing models. However, I don’t think they would make a custom model unless you paid through the nose. With the thousands of dollars in large industrial installations, I don’t think Tom Danley has any interest in the Home Hi-Fi market. I don’t blame him either. We all know how much a circus Hi-Fi audio is. There have been several people trying to get Tom to design a flagship home version of his Synergy, but he has declined. That’s all I have to write about the Synergy.

A member of this site asked about the Synergy horn patent link not working. I'll try to upload the PDF file of the patent for all to view. It is no fun trying to find this patent. It is difficult to search for because it has not yet been approved. I hope the upload works.

Indeed it is a very fine product, in fact very impressive
but I do not know what it has to do with building horns. Strength is not the quality
in my view that is necessary for horns construction. The maternal also can be used
as mold as it sticks to a surface.

Those materials may be interesting to be used as finishing/primer to avoid degradation of the (polymer) concrete horns. And at least one of them can also be applied on wood.
I, of course, do not have idea how any of those products would interfere in the horn sound but would be worth to test in some small horn to know.
Cheers!